I read your reply several times. I don't see that it explains how you have multiple accounts nor does it explain how to combine them (unless Promo codes work differently on UberEats than Uber.)
It was motzio shabbos and had a bunch of siblings which were around in my house, so I asked if they want something to eat, and the reply was yes so......
I used 4 accounts...
Account A-B-C-D , now I used account A as the account to refer B-C-D and now earning $15 in credit to each account since I signed up with a referral code, (so Account B-C-D now all have $15 of credit in each,)and I earn $5 for each referral I send and the person completes their order,so now account A now has a credit of $15(but did not use up that credit yet).
I went ahead and placed an order for each account up to $15 (x3 = 45) now while that order was being prepared I took a shot at the OP's code and worked for each account so now I was able to use another $15 credit in each account(B-C-D now have another $15 each)
You can't use two credits at once rather wait till it's delivered and then use the next promo, so that's what I did next placed another 3 orders(3x$15 = $45 + previous orders of $45 and the unused $15 credit for referring other accounts = $105)
And if your going to ask why didn't you use account A with the ops code and get $15 free as well was because the code wouldn't apply,said it has been used previously when I never ordered Ubereats , so that we will deal with later and get another $15 free...
And they were all 4 different family members account, none of them were a duplicate account for one person....
And for all those with 5-10 accounts under 1 name then you could have enough food for an army...
